In mix preparation and the measuring out of fuel for internal combustion engines, very high requirements are set for both a carburetor and an injection unit as to the content of the exhaust in harmful substances. As we known, high proportions of harmful substances in the exhaust are traced to an insufficient quality of mix, that is, mixing of fuel and combustion air. To obtain a good quality of mix, an optimal mixing of fuel and suction air, a homogeneous distribution of the fuel in the stream of air, and a homogeneous drop size are especially important. Especially in lean engine concepts where one works with a high excess of air, these factors attain still greater importance.
Known means for attaining a good quality of mix are central injection units, such as those described in Kraftfahrttechnische Taschenbuch, 19th edition, VDI Verlag GmbH, Dusseldorf, on Pages 374 and 375. In these devices, an air mixing meter is installed between an air filter and a mix former. In this air amount meter, there may be a damper, a heating wire, or an ultrasonic measuring location. After flowing through the air amount meter, the suction air is led to the mix-forming point. Here, an injection valve is arranged in the suction pipe to which fuel is fed under pressure. The injection valve is equipped with a nozzle, and the fuel is injected through this latter into the suction air stream. In the flow direction of the suction air stream, below the injection valve, is a known choke valve for the regulation of the stream of air or mixture. The feeding of the fuel to the injection valve takes place through a fuel pump. The delivery amount of this pump is determined by a control. The air amount meter serves as sensor for the control.
In addition to the injection valves, spiral scoops, supersonic vibrators, pulsating systems and other devices are sometimes used for improvement of the quality of mix. Injection nozzles for pulsating or air-jacketed systems are technically elaborate in construction and production, and are relatively expensive. The injection valves and nozzles known today cannot assure an ideal thorough mixing of the fuel with the air stream. Moreover, the droplet size of the injected fuel is distributed over a wide spectrum, which in addition to poor mix formation, favors the danger of deposition of fuel on the parts of the mix former. The known difficulties such as the increase of fuel consumption and of harmful substances in the exhaust result from this.
From U.S. Pat. No. 4,044,081 is known a mix-improving device in which an injection valve is combined with a rotary atomizer. A flywheel is arranged in the suction pipe of this device, and namely, before the choke valve in the flow direction of the suction air stream. The flywheel is connected with a rotor and drives the latter. The stream of air flowing through the suction pipe sets the flywheel, and thus the rotor, in rotation. An air line for hot air as well as a pressure line for fuel are introduced into the rotor. In the zone where the two lines discharge into the rotor, one or more eddy chambers are arranged inside in which an intensive mixing of the hot air with the injected fuel should take place. In the peripheral zone of the eddy chamber, nozzle bores are arranged which make possible an outflow of the fuel-air mixture in the direction of the suction air stream. The outflow of the fuel-air mixture through the nozzle bores is promoted by the centrifugal effect of the rotating rotor, while additional openings are also arranged in the suction pipe to obtain an improvement of the thorough mixing of fuel and air. The arrangement of the additional mix improvement devices in the suction pipe makes it clear that even in this device, the same difficulties occur as in the known injection valves without additional rotating mix improvers. The mix formation in the eddy chamber and also the outflow through the nozzle channels are quite difficult to control, and an ideal mix formation can hardly be obtained. The construction design of the device is expensive and hinders the flow of air in the suction pipe.
From German Disclosure No. 2,133,134 is known another carburetor for internal combustion engines with a rotating atomizer. An atomizer pot is set in rotation mechanically from outside. In the center of the atomizing pot is an in-flow opening for fuel and an inset body with a regulating needle. Between the inner wall of the atomizer pot and the inset body is formed a ring-shaped suction channel from which the fuel is sucked into the stream of air. The measuring in of the fuel is difficult here, and very inexact. The additional mechanical rotary drive is expensive and prone to disturbances. This device is intended for a suction carburetor and is not suitable for mixing devices with an injection pump and an injection nozzle. The quality of mix is, in particular, insufficient for the operation of lean engines.